Tier 1 (A): Very Easy
Tier 2 (B): Easy
Tier 3 (C): Medium
Tier 4 (D): Hard

Astra:

Would say she is probably the most skilled agent in the game, and that is due to the amount of IQ, Patience and Game-sense one must have to use her effectively. Very hard for newer players to pick her up. Considering all that has been said, I would place her in Tier 4.

Breach:

Wouldn't say he is entirely easy to pick up, but he could be placed in Tier 1 or Tier 2. However, using him effectively with a team may take some time for newer players, so placing him in Tier 2 seems reasonable.

Brimstone:

All Controllers are hard to learn in their own way, whether that is Viper, Omen, Harbor, Astra or Brimstone. So it is safe to say Brimstone would be classed as B-Tier. This is of course due to him being able to use his molly by default or through lineups, then there are his Stim which is very easy to use. Like all other Controllers, his smokes need to be placed correctly to use them effectively and in the benefit of the team, but if not, could cost a round and provide support for the enemy team.

Chamber:

Would place Chamber in Tier 2, maybe Tier 1. Yes his Deagle may require a headshot to kill someone, but his Operator counteracts this by letting him one shot in the torso for free anyway. So who cares. Bad agent either way to be fair. Those who pick him up are cry baby andys that just want him buffed again because they are used to him being broken and never played a balanced agent before.

Cypher:

Got to place my home boy in Tier 3. Deserves extra credit for being bullied with every Riot Trailer. Genuinely though, Cypher is easy to pick up when playing him for the first time which brings him to Tier 1; however, to maximise his play potential, players must learn where to place his trips properly, so that they can fully benefit off of them. Then ofc he deserves T3 for being bullied.

Fade:

Would say she is borderline Tier 1, but probably deserves Tier 2. Players that pick her up would know how to use her straight away, but her kit requires some level of game sense to know how to fully maximise her kit to its full potential. Such as combos, timings and just gathering intel for their team.

Gekko:

Ah yes the new Agent. After playing him for some time I thought he would be Tier 4, due to the patience and timings needed to effectively play him, but that ain't the case. Been 3 days and many players have seemed to already know how to play him with decent skill. If he didn't need to spend 2-3s picking his abilities up each time, I would say he deserves Tier-2. Although, due to throwing his abilities and needing to pick them up every time, the player needs to ensure they are safe enough to pick them up, as well as make sure his abilities aren't deep into enemy territory. So proper usage of his abilities to make sure he gets them back, takes him to Tier-3.

Harbor:

Similar to Brimstone, he requires some knowledge on smoke placement to play effectively. However, due to Harbor's aggressive kit, he can easily take a site if played correctly and with his team. So I would say he deserves Tier 2 at most.